The present invention relates to ferromagnetic thin-film memories and, more particularly, to ferromagnetic thin-film memories in which states of the memory cells based on the magnetization direction therein are determined through inductive sensing.
Digital memories of various kinds are used extensively in computers and computer system components, digital processing systems, and the like. Such memories can be formed, to considerable advantage, based on the storage of digital bits as alternative states of magnetization in magnetic materials in each memory cell, typically thin-film materials. These films may be thin ferromagnetic films having information stored therein based on the direction of the magnetization occurring in those films, this information being obtained either by inductive sensing to determine the magnetization state, or by magnetoresistive sensing of such states. Such ferromagnetic thin-film memories may be conveniently provided on the surface of a monolithic integrated circuit to thereby provide easy electrical interconnection between the memory cells and the memory operating circuitry in the monolithic integrated circuit.
Ferromagnetic thin-film memory cells, if they are to be provided in a monolithic integrated circuit as indicated above, must be made very small and packed very closely together to achieve a significant density of stored digital bits. These requirements lead to problems with inductively sensed memories because the signal levels to be inductively sensed decline with reduced thicknesses and widths for the magnetic thin-film portions used in each memory cell to store a bit as there is then less flux linkage to be inductively sensed. Thus, there is a desire to have an inductively sensed magnetic memory which provides adequate sensing signal magnitudes to be sensed by circuits in a monolithic integrated circuit, and which can be fabricated as part of such a monolithic integrated circuit.